Automatically controlled weigh feeding apparatus

ABSTRACT

Disclosed herein is an automatically controlled weigh feeding system including a container prefilled with a substance, a device for discharging the substance from the container at a controllable rate, apparatus for weighing the container and its contents and for producing an electrical signal proportional to that weight, apparatus actuated by the electrical signal for controlling the discharge of the substance from the container, and a detector circuit actuated by the electrical signal for producing an output which is responsive to predetermined excessive excursions of the electrical signal for locking the discharge control apparatus against deviation during the time of the excessive excursion. .Iadd.

This is a continuation-in-part of our copending application Ser. No.345,587, filed Mar. 28, 1973, which issued as U.S. Pat. No. 3,889,848and which, in turn, is a continuation-in-part of a parent applicationSer. No. 274,844, filed July 25, 1972 (and later abandoned). .Iaddend.

This invention relates to weigh feeding systems and it is particularlyapplicable to apparatus for feeding particulate solid material. Systemsconstructed according to the present invention are particularly adaptedamong other possible uses for accurately weigh feeding a wide variety ofsubstances including dry materials regardless of whether the material isfree-flowing, sluggish, or pressure sensitive, and ranging fromamorphous powders to flakes, pellets, chunks and even fibers, as well asliquids.

Various controlled weigh feeding systems have been known in the past, asfor example, the system disclosed in U.S. Pat. No. 3,494,507, wherein aweighing device is incorporated for providing an output signal which isused as one of the parameters for controlling the discharge rate of thesystem. Thus, in the above-cited patent, the contents of a container aredischarged onto a conveyor moving at a known rate, and the weight of theconveyor is detected, so that the numerical values corresponding to theweight of the conveyor and the speed thereof can be combined to providea discharge rate signal to an indicator device. It has been found,however, that the system as disclosed in the above-cited patent ishighly effective except where extremely low rates and optimum accuracyare required, wherefore it is desirable to provide a weigh feedingsystem having a discharge rate which can be controlled to a high degreeof accuracy, and which can be adjusted from a fraction of a pound perhour upwards.

The present invention is closely related to U.S. Pat. No., 3,889,848issued June 17, 1975, and is directed to improvements of the apparatusdescribed and claimed therein. In accordance with this application,there is provided a weigh feeding apparatus wherein the discharge rateof a fluid substance from a container is maintained at a predeterminedconstant value. The container and its contents are weighed, and anelectrical signal is produced which signal has an amplitude proportionalto the weight of the container and its contents. This electrical signal,which varies as the contents of the container are discharged, isdifferentiated and applied to a comparator circuit together with areference signal, wherefore the output of the comparator circuit may beused to control said discharge rate of the substance as it is fed fromthe container. The comparator output is applied to a signal generatorfor producing a motor drive signal for a DC motor having its outputshaft connected to drive a device for discharging the substance from thecontainer. That signal generator may comprise a pulsing circuit forcontrolling a pair of SCR's which are disposed in a rectifying bridgecircuit connected between an AC voltage source and the input of the DCmotor. Accordingly, the speed of the motor is controlled by the pulsingcircuit, which, in turn, is controlled by the algebraic sum of theoutput signal of a tachometer generator which is coupled directly to themotor shaft, and the output signal from the comparator. It can be seenthat the above-described apparatus provides an accurate weigh feedingsystem, whereby the feeding rate may be maintained at a constant value,and wherein the predetermined feeding rate may be adjusted by adjustingthe value of the reference signal source.

Additionally, the output of the weighing device may be applied to a pairof differential amplifier circuits, along with a pair of referencevoltage inputs, for determining when the contents of the containervaries above and below desired maximum and minimum fill levels for thecontainer. That is, circuitry is provided for automatically refillingthe container when the weight of the substance therein reaches thedesired minimum weight, and for terminating the filling process for thecontainer when the fluid substance therein reaches the desired maximumweight. Such circuitry includes means for maintaining the discharge rateof the container at the constant rate equal to the instantaneous ratethereof immediately preceding energization of the filling device for thecontainer. Particularly, the pair of differential amplifier circuits arecoupled to a pair of relay driver circuits for controlling a relaycircuit to energize the filling device when the substance in thecontainer reaches the minimum weight, and for maintaining that fillingdevice in an energized state until the container is refilled to itsmaximum desired level. The relay circuit is also coupled to thecomparator circuit, for controlling the latter to produce a constantoutput during the refilling process for the container, therebymaintaining the discharge rate of the container at the value of theparticular discharge rate thereof immediately preceding energization ofthe filling device.

As pointed out in said U.S. Pat. No. 3,889,848, in certain installationsthere exists a possibility of physical forces impinging upon the weighfeeder from an external source, such as wind or air currents, physicalcontact with the weigh feeder by operating personnel, or the like, forexample. These forces cause the weigh feeder to move at a rate that isother than that resulting from the linear discharge of the contents ofthe container. Because such additional movement, i.e. acceleration, isan error and has no direct relationship to the actual discharge ofmaterial from the container, the control system could continue toperform its corrective function utilizing the erroneous output signalfor comparison with the fixed set point reference signal derivative. Theaforementioned patent application discloses one means for preventingsuch excessive and abnormal movements of the weigh feeder scale fromgrossly affecting or disturbing the normal operation of the system tothereby prevent large excursions of the output feed rate. The presentinvention is directed to a new improved means for accomplishing thisobjective, which is of simplified construction and, hence, moreeconomical.

In accordance with the invention there is provided a weigh feedingsystem comprising a container prefilled with a substance, a device fordischarging the substance from the container at a controllable rate, andapparatus for weighing the container and its contents and for producingan electrical signal proportional to that weight. In addition, saidsystem is further characterized by apparatus actuated by said electricalsignal for controlling the discharge of the substance from thecontainer, and detector circuit means actuated by said electrical signalfor producing an output which is responsive to predetermined excessiveexcursions of the electrical signal for locking the discharge controlapparatus against deviation during the time of the excessive excursion.

It will be appreciated that due to the double auger mechanism employedin the system of the present invention, accurate volumetric output ismaintained even during the periods when the electrical system istemporarily "locked out" due to some external disturbance, or during arefill cycle. Such double auger mechanism is disclosed in U.S. Pat. Nos.3,186,602 and 3,439,836, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate several embodiments of theinvention. In such drawings:

FIG. 1 is a diagrammatic view of a combination of elements embodied inthe invention;

FIG. 2 is a block diagram of the control circuitry embodied in thecombination shown in FIG. 1;

FIG. 3 is a schematic diagram of the comparator circuitry shown in blockform of FIG. 2;

FIG. 4 is a schematic diagram of the motor drive signal generator shownin block form in FIG. 2;

FIG. 5 is a schematic diagram of the signal holding circuit shown inblock form in FIG. 2;

FIG. 6 is a schematic diagram of the detector circuitry shown in blockform in FIG. 2; and

FIG. 7 is a schematic diagram of the relay circuit shown in block formin FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The volumetric feeding apparatus of this invention, as showndiagrammatically in FIG. 1, includes a container 10 for a quantity ofmaterial, wherein the container has a discharge device 12 connectedthereto for feeding the substance out of the container and through theconduit 14. As illustrated, a motor 16 connected through agear-reduction device 18 is provided for driving the discharge device12, which, as illustrated in FIG. 1 may comprise an auger mechanism asdescribed in detail in U.S. Pat. No. 3,186,602, issued June 1, 1965. Theentire feeding apparatus, including the container, the discharge device,the motor, and the gear-reduction device, is mounted on a scale 20,which may comprise a structure as described in detail in U.S. Pat. No.3,494,507, issued Feb. 10, 1970.

In accordance with the invention there is provided a detecting device asfor example, a linearly variable differential transformer (LVDT) 22,coupled to the scale for providing an electrical signal having anamplitude which is proportional to the weight of the container and itscontents. That is, as the contents of the container 10 are discharged, arelative movement occurs between the windings and the core of the LVDT,thereby causing a varying output voltage proportional to the varyingweight of the container and its contents. Thus, as the substance isdischarged from the container the .[.LDVT.]. .Iadd.LVDT.Iaddend.provides an electrical signal which varies in response to suchdischarge. The electrical signal from the LVDT is applied to controlcircuitry 24 by a conductor 26, and the control circuitry also receivesa tachometer signal from the motor 16 as a second input thereto. Thepurpose of the control circuitry 24 is to provide an output signal on aconductor 30 which is used to control the speed of the motor 16, therebycontrolling the discharge rate of the substance from the container 10.In particularly, the control .[. cicuitry.]. .Iadd.circuitry.Iaddend.operates to maintain the motor speed at a value which providesa desired specific discharge rate for the substance in response to thedetection of the actual discharge rate as derived from the LVDT signal,and in response to the actual speed of the motor as determined by thetachometer signal.

As illustrated in FIG. 1, the invention further comprises a secondvolumetric feeding device 32, also having a container 34, and an augerdischarge mechanism 36 for operation to automatically refill thecontainer 10 in order to maintain the fill level of the container 10between predetermined desired levels. The discharge device 36 is drivenby a constant speed motor 38 which is energized by an output signal fromthe control circuitry as coupled through a conductor 40.

In the embodiment illustrated in FIG. 1, the containers 10 and 34 anddischarge devices 12 and 36 are for all types of substances comprisingsolid particles, but it is to be understood that the combination asdescribed above, may be used also for controlling the discharge ofliquid substances from a container, wherefore the augers would bereplaced by pumps.

FIG. 2 illustrates a block diagram of the control circuitry 24 whichforms a part of the combination shown in FIG. 1, wherein the LVDT outputsignal is applied to a rectifier 42 for converting the AC signal fromthe LVDT into a DC signal, which DC signal is then applied to anamplifier 44. The amplified DC signal is coupled through a conductor 46to a differentiator 48 which provides an output signal directlyproportional to the rate of discharge of the substance from thecontainer 10. That is, the LVDT output signal, which comprises alinearly variable electrical signal when the substance is discharged ata constant rate, is differentiated to provide a steady state signalwhich is directly and linearly proportional to said discharge rate.

The output of the differentiator 48 is coupled along a conductor 50 andthrough a signal holding circuit 52 to a flow rate indicator 54 for thepurpose of providing a visual indication of the detected flow rate ofthe substance being fed from the container 10.

The output of the differentiator 48 is also applied as an input to acomparator circuit 56, such comparator circuit also having a referencevoltage signal as a second input 58 thereto, coupled from a voltagesource 60, for the purpose of providing a comparison output signal asrelated to the two input signals. Thus, the reference voltage signal maybe set to correspond to the desired discharge rate for the substance,whereby the output 62 from the comparator circuit provides an errorsignal as determined by any difference between the reference voltagesignal and the actual discharge rate as indicated by the differentiatoroutput 50. Then, the error signal provided by the comparator output 62is applied to a motor drive signal generator 64 algebraically with thetachometer output signal 28, and the motor drive signal generator thenproduces an output signal for application to the drive motor.Accordingly, when the actual discharge rate of the substance varies fromthe desired discharge rate thereof, the error signal from the comparator56 causes the motor drive signal generator 64 to generate an outputwhich alters the speed of the drive motor 16, thereby changing thedischarge rate until it corresponds with the desired discharge rate.

The amplified DC signal corresponding to the LVDT signal is also appliedthrough the conductor 46 as a first input to a pair of differentialamplifiers 66 and 68, each of which has a second input connected todifferent reference voltage source output circuits of a second referencevoltage source 70. The purpose of the pair of differential amplifiers66, 68 is to provide output signals indicating when the quantity ofsubstance within the container 10 falls below the desired minimumquantity, and when the quantity of such substance exceeds a desiredmaximum quantity. Thus, the reference voltage source 70 provides outputsignals corresponding to these predetermined desired maximum and minimumquantities. The outputs from the differential amplifiers are coupledthrough conductors 66a and 68a, and through respective relay drivercircuits 72, 74 and applied as inputs to a relay circuit .[.76.]..Iadd.76' .Iaddend.for controlling the operation of the motor 38 bymeans of a signal coupled along conductor 40. As described above,operation of the motor 38 causes the container 10 to be refilled fromthe container 34. Accordingly, the relay circuitry is connected toenergize the motor 38 when the minimum detecting differential amplifier66 generates an output in response to the indication of the minimumquantity of substance, and such relay circuitry maintains the drivemotor 38 in an energized state until a signal is received from themaximum detecting differential amplifier 68 indicating that the filllevel of the container 10 has reached the desired maximum level. Uponcompletion of the refill process, the motor 38 is deenergized, but it isto be understood that the discharge of the substance from the container10 is continuous throughout the period before, during, and after therefill process.

An output 78 from the relay circuitry .[.76.]. .Iadd.76' .Iaddend.isalso coupled to the signal holding circuit for causing that circuit tomaintain the flow rate indication at the value thereof immediatelypreceding initiation of the refilling process; and a third output 80from the relay circuitry .[.76.]. .Iadd.76' .Iaddend.is applied to thecomparator circuit 56 in order to maintain the comparison output signalat the value thereof immediately preceding such refill process. That is,the second and third outputs from the relay circuit .[.76.]. .Iadd.76'.Iaddend.prevent grossly erroneous readings on the flow rate indicator54, and prevent erratic control of the motor drive signal generator 64while the container 10 is being refilled.

The details of the comparator circuitry 56 are shown in schematic formin FIG. 3, wherein the input 58 from the reference signal source 60 isapplied to one input terminal of a unity gain follower amplifier 82,which, for example, may be provided by an integrated circuit such as aBurr-Brown Model No. 3500 device. The connections of the variousterminals of the unity gain follower amplifier 82 are as shown in FIG.3, wherein positive and negative voltage sources V+ and V- are connectedthereto, and wherein the output 82a is fed back to one of the inputterminals. The output 82a of the unit gain follower amplifier is alsoconnected to one end of a potentiometer 84 which has its other endconnected to the output of a unity gain inverter amplifier 85 whoseinput is connected to the output 50 of the differentiator circuit 48.The wiper arm 84a of the potentiometer is connected to one input 86a ofan operational amplifier 86 connected in an inverting feedback mode. Thedevice forming the operational amplifier may comprise a Burr-Brown ModelNo. 3267/12 C amplifier device. Then, the output of the operationalamplifier is connected through a set of relay contacts 88a to the input90a of an integrating circuit 90, which may comprise, for example, aBurr-Brown operational amplifier Model No. 3308/12C device.

In operation, if the reference voltage signal at 58 is greater than theinput signal from the differentiator, more current will flow into theoperational amplifier 86, thus causing the output thereof to swingnegative. A negative input to the integrator 90 causes its output to gopositive, and the time required to reach full output is determined bythe input RC network 92 of the integrator and the amplitude of thevoltage applied thereto. On the other hand, when the differentiatoroutput voltage is higher than the reference signal, the amplifier outputwill swing positive thus causing the integrator output to decrease involtage. In this manner, an error control voltage proportional to thecomparison between the actual and desired flow rates is generated by thecomparator, and the adjustable RC network 92, provided between theoutput of the amplifier 86 and the input of the integrator 90, providesa fast increase in the comparator output when a large error isintroduced. The zener diode 94 is for clamping the comparator outputvoltage between a predetermined positive voltage and a voltage of about-0.2 volts as determined by the diode 96.

When the relay contacts 88a are opened, the integrator maintains aconstant output voltage at the conductor 62 due to the feedbackcapacitor 98, since the decay of that output voltage is primarilydetermined by the leakage of the feedback capacitor and the inputimpedance of the operational amplifier forming the integrator 90. Thus,during normal operating conditions, the relay contacts 88a remain closedso that a continuously corrected error voltage is produced. However,during the period in which the container 10 is being refilled, the relaycontacts 88a are opened, as described below, so that the output signalon the conductor 62 is maintained at the value immediately preceding theopening of contacts 88a.

A difference signal derived from the tachometer output signal on theline 28 and the comparison signal on the line 62 is applied to aterminal 100 of an amplifier 102 connected to a uni-junction pulsingcircuit 104, as shown in FIG. 4. FIG. 4 also illustrates a motorarmature connection 106, and a field connection 108 for the DC motor 16,wherein the armature and field are connected to a rectifier circuit110a, which in turn receives an output power signal from an AC source,such as a 110 volt, 60 Hz. supply 112. The AC source 112 is also coupledto a primary winding of a transformer 114, the secondary of which isconnected through a unfiltered full-wave rectifier 116 to provide thesupply voltage for uni-junction pulse circuit 104 and amplifier 102.Thus, the uni-junction pulser circuit 104 is synchronized with the ACsource applied to the rectifier circuit 110. The output of theuni-junction pulser circuit is connected to the primary 118a of a pulsetransformer having a pair of secondaries 118b and 118c connectedrespectively to the gate electrodes to a pair of SCR devices 110b and110c connected in the full wave bridge which provides the rectifiercircuit 110a.

Accordingly, the drive signal applied to the armature of the DC motor isderived from the rectifier circuit 110a and is controlled by the pulsingof the uni-junction transistor circuit 104, wherein the timing of theuni-junction transistor circuit is dependent upon the input 100 to theamplifier portion 102 thereof.

A commutating diode is connected across the rectifying bridge of thecircuit 110a to maintain a flow of armature current when the SCR's 110band 110c are turned off during the negative half cycle of the linevoltage. Also, the diodes 120a and 120b in the circuit 110a provide aconstant DC voltage for the motor field connection 108.

Again, it is seen that by varying the timing pulses from theuni-junction firing circuit 104, the SCR's 110b and 110c will becontrolled to turn on at a varying point with respect to the anodevoltages, thus providing a varying DC output for the motor armature, inorder to control the speed of the DC motor.

FIG. 5 illustrates an embodiment of the signal holding circuit 52, whichmay comprise, for example, an operational amplifier such as a Burr-BrownModel No. 3309/12C device, which provides a high input impedance FETamplifier 122 having an extremely low leakage capacitor 124 in itsfeedback loop. Relay contacts 88b connect the negative input of theamplifier to the output 50 of the differentiator 48, whereby the device52 operates as a unity gain invertor. That is, while the relay contacts88b are closed, the differentiator output at line 50 is coupled to theindicator 54 to give an indication of the actual discharge rate.However, when the relay contacts 88b are opened, the value of the outputvoltage for the circuit 52 remains at the last value of the input levelat 50 due to the presence of the low leakage capacitor 124 in thefeedback loop. Accordingly, when the relay circuit .[.76.]. .Iadd.76'.Iaddend.operates to initiate the refill process for the container 10,the indicator device 54 is supplied with a constant voltage equivalentto the output from the signal holding circuit 52 immediately prior tothe initiation of such refilling process, and such constant voltage ismaintained until termination of the refill process and the closing ofrelay contacts 88b.

FIG. 7 illustrates a representative relay circuit .[.76.]. .Iadd.76'.Iaddend.wherein a motor drive power source V is coupled through theline 40 to the refill motor 38 through a set of relay contacts 88c,which contacts are controlled by a relay coil 88 having one endconnected to a common potential point, and having its other endconnected to the power source V through a pair of normally openedcontacts 126a of a relay having its coil 126 connected to the relaydriver circuit 72 which is controlled by the minimum detectingdifferential amplifier 66. The coil 88 is also connected to the powersource V through the relay contacts 128a of a relay having its coil 128controlled by the maximum detecting differential amplifier relay drivercircuit 74 and through a pair of slave contacts 88d.

In operation, when the minimum detecting differential amplifier 66provides an outut signal, the relay driver circuit 72 causes the relaycoil 126 to energize, thereby connecting the voltage source to the coil88 of the control relay, thus causing it to energize. Accordingly, therefill process is initiated due to the closing of the relay contacts88c. When the fluid substance level in the container rises sufficientlyto cause deenergization of the minimum detecting circuit relay 126, thecontrol relay coil 88 remains energized due to the slave contacts 88d.Also, the signal holding circuit 52 and the comparator circuit 56 arelocked in their respective steady state conditions as described abovedue to the actuation of the relay contacts 88a and 88b which are shownin dotted lines in FIGS. 3 and 5, and which are connected by theconductors 78 and 80 to the respective signal holding and comparatorcircuit. However, when the maximum detecting differential amplifier 68generates an output signal through the relay driver circuit 74 to themaximum detecting relay 128, then the energization circuit for thecontrol relay coil 88 is opened, and the refill process is terminateddue to the opening of the relay contacts 88c.

It will be appreciated that the weigh feeder may be subject to anexternal force impinging upon the weigh feeder system, thereby alteringthe constant upward movement, or velocity, of the system. Thisalteration results in either acceleration or deceleration of the system,depending upon the direction of the impinging external force. Thepresent invention is directed to the elimination of large excursions ofthe output feed rate.

As best seen in FIG. 2, there is provided detector circuitry 150 whichreceives the amplified DC signal corresponding to the LVDT signalthrough the conductor 46. FIG. 6 illustrates an embodiment of thedetector circuitry 150, which comprises an alternating current coupled,adjustable gain amplifier with frequency response 164, which, forexample, may be provided by the National Semiconductor Corp., Model No.LM324N. The amplifier 164 has an input terminal 166 which is connectedto the conductor 46 through an input capacitor 168 and to ground througha resistor 170. A feedback capacitor 172 is connected between the outputterminal 174 and a second input terminal 176 of the amplifier 164. Also,the output terminal 174 of the amplifier is coupled to a feedbackpotentiometer 178 disposed between two resistors 180 and 182. The otherterminal of resistor 182 is connected to ground through a capacitor 184and a resistor 186 connected in parallel. The sliding contact or wiperarm 188 of the potentiometer 178 is coupled to the input terminal 176 tocontrol the gain of the amplifier 164. Thus, the wiper arm may beconsidered to be a reference signal source. The output terminal 174 ofthe amplifier is coupled to a conductor 158 through an output capacitor190.

Thus, any acceleration, deceleration or abnormal disturbance in theweigh feeder system, as reflected by the signal received by the detectorcircuitry causes it to emit an output signal 158. As seen in FIG. 2, theoutput 158 from the detector circuitry 150 is coupled through a relaydriver circuit 160 to a relay circuit 76'. This relay circuit is similarto relay circuit 76 .Iadd.of the abovementioned patent 3,889,848,.Iaddend.but has added thereto a relay coil 162, FIG. 7, which whenenergized opens normally closed contacts 88a' and 88b'. Thus, inoperation, when the detector circuitry 150 provides an output signal,corresponding to an excessive acceleration or deceleration of the weighfeeder system, the relay driver circuit 160 causes the relay coil 162 toenergize, thereby opening relay contacts 88a' and 88b'. These contactsare connected by the conductors 78 to 80 to the respective signalholding and comparator circuits. Consequently, the output signal on theconductor 62 is maintained at the value immediately preceding theopening of contacts 88a' in the same manner as that describedhereinbefore in connection with contacts 88a. When the relay contacts88b' are opened, the value of the output voltage for the circuit 52remains at the last value of the input level at 50 and, hence, theindicator device 54 is supplied with a constant voltage equivalent tothe output from the signal holding circuit 52 immediately prior to theinitiation of the excessive deviation, and such constant voltage ismaintained until termination of the excessive acceleration ordeceleration condition and the closing of the relay contacts 88b',thereby returning the system to normal operation, in the same manner asthat described hereinbefore in connection with contacts 88b.

From the foregoing disclosure it can be seen that the instant inventionprovides an improved weigh feeding apparatus, wherein the discharge rateof a substance from a container may be maintained at a constant valueselected from a range of values, and wherein the container may beautomatically refilled during the continuous discharge of the substance,and wherein excessive excursions of the system are eliminated.

Although a specific representative structure has been described hereinfor purposes of explanation, reference should be had to the appendedclaims in determining the scope of this invention.

We claim:
 1. A weigh feeding apparatus comprising a container for aprefilled substance, means for discharging the substance from thecontainer at a controllable rate, means for weighing the container andits contents and for producing an electrical signal proportional to theweight, means actuated by said electrical signal for controlling thedischarge of the substance from the container, detector circuit meansactuated by said electrical signal for producing an output which isresponsive to predetermined excessive excursions of said electricalsignal, and means responsive to said output for locking the dischargecontrol means against deviation during the time of said excessiveexcursion. .[.2. A weigh feeding apparatus according to claim 1 whereinsaid detector circuit means comprises an adjustable gain amplifier..].3. A weigh feeding apparatus comprising a container for a prefilledsubstance; means for discharging said substance from the container at acontrollable rate; means for weighing said container prefilled with saidsubstance; means coupled to said weighing means for producing anelectrical signal proportional to the weight determined by said weighingmeans; first circuit means having an output terminal and having an inputcoupled to said electrical signal means for providing a rate signal atsaid output terminal which is proportional to the discharge rate of saidsubstance from said container; control signal generating means having anoutput terminal, and having an input terminal connected to said firstcircuit means output terminal, wherein said control signal means is forgenerating at its output terminal a discharge control signal which is afunction of said rate signal; and means coupled between said controlsignal generating means output terminal and said means for dischargingsaid substance, for controlling the discharge rate of said dischargingmeans in response to said discharge control signal, detector circuitmeans having an output terminal and having an input coupled to saidelectrical signal means for producing an output which is responsive topredetermined excessive excursions of said electrical signal, meanscoupled between the output terminal of said detector circuit means andsaid control signal generating means for maintaining said control signalconstant during the time of said excessive excursions. .[.4. A weighfeeding apparatus according to claim 3 wherein said detector circuitmeans comprises an alternating current coupled, adjustable gainamplifier with frequency response..]. .[.5. A weigh feeding apparatusaccording to claim 3 wherein said detector circuit means comprises analternating current coupled amplifier, said amplifier having an inputterminal connected to the input of the detector circuit means through aninput capacitor and to ground through a resistor, a feedback capacitorconnected between an output terminal and a second input terminal of saidamplifier, said output terminal of the amplifier being coupled to afeedback potentiometer disposed between two resistors, the otherterminal of one of said resistors being connected to ground through acapacitor and resistor connected in parallel, and the wiper arm of saidpotentiometer being coupled to said second input terminal of saidamplifier to control the gain of the amplifier, and said output terminalof said amplifier being coupled through an output capacitor to saidoutput terminal of said detector circuit means..].
 6. Apparatus forfeeding particulate solid material comprising a container for a quantityof said particulate solid material; means for discharging saidparticulate solid material from the container at a controllable rate;means for weighing said container prefilled with said particulate solidmaterial; means coupled to said weighing means for producing .[.and.]..Iadd.an .Iaddend.electrical signal proportional in amplitude to theweight determined by said weighing means; differentiator circuit meanshaving an output terminal and having an input coupled to said electricalsignal means, wherein said differentiator circuit means is fordifferentiating said electrical signal to provide a rate signal at saidoutput terminal which is proportional in amplitude to the discharge rateof said particulate solid material from said container; control signalgenerating means having an output terminal, and having an input terminalconnected to said differentiator circuit means output terminal, whereinsaid control signal means is for generating at its output terminal adischarge control signal which is a function of the amplitude of saidrate signal; and means coupled between said control signal generatingmeans output terminal and said means for discharging said particulatesolid material for controlling the discharge rate of said dischargingmeans in response to said discharge control signal, electricallyactuatable means for refilling said container, first detector means fordetecting when the quantity of said particulate .[.said.]. .Iadd.solid.Iaddend.material in said container is less than a desired minimumquantity, second detector means for detecting when the quantity of saidparticulate solid material in said container is greater than a desiredmaximum quantity, switching means coupled between said first and seconddetector means and said means for refilling said container forenergizing said electrically actuatable refilling means in response todetection by said first detector means .[.to.]. .Iadd.of .Iaddend.saiddesired minimum quantity, and for maintaining said refilling means insaid energized state until detection by said second detector means ofsaid desired maximum quantity, detector circuitry means having an outputterminal and having an input coupled to said electrical signal means forproducing an output which is responsive to predetermined excessiveexcursions of said electrical signal means, means coupled between theoutput terminal of said detector circuit means and said control signalgenerating means for maintaining said control signal constant during thetime of said excessive excursions.
 7. Apparatus for feeding particulatesolid material comprising a container for a quantity of said particulatesolid material; means for discharging said particulate solid materialfrom the container at a controllable rate; means for weighing saidcontainer prefilled with said particulate solid material; means coupledto said weighing means for producing an electrical signal proportionalin amplitude to the weight determined by said weighing means;differentiator circuit means having an output terminal and having aninput coupled to said electrical signal means, wherein saiddifferentiator circuit means is for differentiating said electricalsignal to provide a rate signal at said output terminal which isproportional in amplitude to the discharge rate of said particulatesolid material from said container; control signal generating meanshaving an output terminal, and having an input terminal connected tosaid differentiator circuit means output terminal, wherein said controlsignal means is for generating at its output terminal a dischargecontrol signal which is a function of the amplitude of said rate signal;and means coupled between said control signal generating means outputterminal and said means for discharging said substance, for controllingthe discharge rate of said discharging means in response to saiddischarge control signal, detector circuit means having an outputterminal and having .[.and.]. .Iadd.an .Iaddend.input coupled to saidelectrical signal means for producing an output signal which isresponsive to a predetermined excessive excursion of said electricalsignal, voltage sensing circuit means coupled between the outputterminal of said detector circuit means and said control signalgenerating means for maintaining said control signal constant during thetime of said excessive excursion.
 8. Apparatus for feeding particulatesolid material, comprising a container for a quantity of saidparticulate solid material; means for discharging said particulate solidmaterial from the container at a controllable rate; means for weighingsaid container prefilled with said particulate solid material; meanscoupled to said weighing means for producing an electrical signalproportional in amplitude to the weight determined by said weighingmeans; differentiator circuit means having an output terminal and havingan input coupled to said electrical signal means, wherein saiddifferentiator circuit means is for differentiating said electricalsignal to provide a rate signal at said output terminal which isproportional in amplitude to the discharge rate of said particulatesolid material from said container; control signal generating meanshaving an output terminal, and having an input terminal connected tosaid differentiator circuit means output terminal, wherein said controlsignal means is for generating at its output terminal a dischargecontrol signal which is a function of the amplitude of said rate signal,and means coupled between said control signal generating means outputterminal and said means for discharging said substance, for controllingthe discharge rate of said discharging means in response to saiddischarge control signal; said means for producing said electricalsignal being a linearly variable differential transformer; said meanscoupled between said discharging means and said control signalgenerating means including an electric motor for driving saiddischarging means; and said control signal generating means including areference signal source, a comparator having first and second inputsconnected respectively to said reference signal source and saiddifferentiator circuit means output terminal, and having an output forproviding a comparison signal in response to said signals from saidreference source and differentiator circuit means, and motor drivesignal generating means having an input connected to said comparatoroutput, and having an output which provides said discharge controlsignal for controlling the speed of said motor; detector circuit meanshaving an input connected to said electrical signal means for producingan output signal which is responsive to a predetermined excessiveexcursion of said electrical signal, voltage sensing circuit meanshaving an input coupled to an output terminal of said detector circuitmeans, .[.and.]. .Iadd.an .Iaddend.indicating meter for providing avisual indication of the discharge rate of said fluid substance as it isdischarged from the container, .Iadd.and .Iaddend.signal holding meanshaving an input coupled to the differentiator circuit means output toprovide an indicating signal to said indicating meter, said voltagesensing circuit means having an output coupled to said signal holdingmeans and said comparator for completing feedback paths in said signalholding means and comparator during the time that said detector circuitmeans detects said excessive excursion for the purpose of maintainingconstant outputs from said comparator and signal holding means duringsaid time. .Iadd.9. A weigh feeding apparatus comprising a container fora prefilled substance, means for discharging the substance from thecontainer at a controllable rate, means for weighing the container andits contents for producing an electrical signal proportional to theweight, said electrical signal exhibiting excessive excursions inresponse to disturbances impinging on said weighing means, meansactuated by said electrical signal for controlling the discharge of thesubstance from the container, detector circuit means actuated by saidelectrical signal for producing an output which is responsive topredetermined excessive excursions of said electrical signal, and meansresponsive to said output for locking the discharge control meansagainst deviation during the time of said predetermined excessiveexcursions. .Iaddend. .Iadd.10. Weigh feeding apparatus as in claim 9,wherein said detector means produces an output for each excursion ofsaid electrical signal which has an acceleration or deceleration inexcess of a predetermined value, and said responsive means locks thedischarge control means against deviation while each said excessiveexcursion continues. .Iaddend. .Iadd.11. Weigh feeding apparatus as inclaim 10, wherein said discharge control means includes differentiatorcircuit means actuated by said electrical signal for producing a secondelectrical signal which is proportional to the actual rate of dischargeof said substance from said container, and wherein said apparatus alsoincludes a discharge rate indicator actuated by said second electricalsignal for displaying the actual rate of discharge of the substance fromthe container, said discharge rate indicator displaying a constant valuewhile the predetermined excessive excursion of the electrical signalcontinues. .Iaddend. .Iadd.12. Weigh feeding apparatus as in claim 11,wherein said discharging means includes a mechanism for moving saidsubstance and a motor for driving said mechanism, and wherein saiddischarge control means also includes circuit means for establishing athird electrical signal indicative of the desired discharge rate, acomparison circuit for receiving and comparing said second and thirdelectrical signals to produce a fourth electrical signal which isproportional to the difference between said second and third signals,further circuit means for combining said fourth signal with a fifthelectrical signal representative of the existing speed of said motor toproduce a sixth electrical signal having a value responsive to therelative values of said fourth and fifth signals, and circuit means fordelivering said sixth electrical signal to said motor to control thespeed thereof. .Iaddend. .Iadd.13. A weigh feeding apparatus comprisinga container for a prefilled substance, means for discharging thesubstance from the container at a controllable rate, first circuit meansfor establishing a first electrical signal indicative of the desireddischarge rate, means for weighing the container and its contents andfor producing a second electrical signal proportional to the weightthereof, means actuated by said second electrical signal fordifferentiating said second signal to produce a third electrical signalrepresentative of the actual rate of discharge of said substance fromthe container and for controlling the discharge rate in accordance withthe relative values of said first and third electrical signals, saiddischarge control means supplying a control signal to said dischargingmeans, second circuit means for detecting disturbances sensed by saidweighing means which occur at a rate which is faster than changes insaid actual discharge rate, said second circuit means including detectorcircuit means actuated by said second electrical signal for producing anoutput signal which is responsive to predetermined excessive excursionsof said second electrical signal, and means responsive to said outputsignal for locking the discharge control means against deviation duringthe time of said predetermined excessive excursions. .Iaddend. .Iadd.14.A weigh feeding apparatus as in claim 13, wherein, during the time ofthe predetermined excessive excursions, said responsive means locks thedischarge control means at the discharge rate set by the immediatelypreceding control signal supplied to the discharging means. .Iaddend..Iadd.15. A weigh feeding apparatus comprising a container for aprefilled substance, means for discharging the substance from thecontainer at a controllable rate, means for weighing the container andits contents and for producing an electrical signal proportional to theweight, said electrical signal exhibiting excessive excursions inresponse to disturbances impinging upon said weighing means, meansactuated by said electrical signal for controlling the discharge of thesubstance from the container, sensing circuit means responsive to saidelectrical signal for sensing when said weight reaches a predeterminedminimum and when it reaches a predetermined maximum, refill meansresponsive to said sensing circuit means for initiating a refill of saidcontainer, while the discharge of substance from said containercontinues, when the weight has reached said predetermined minimum, andfor discontinuing the refill operation when the weight has reached saidpredetermined maximum, detector circuit means actuated by saidelectrical signal for producing an output signal which is responsive topredetermined excessive excursions of said electrical signal, and meansresponsive to said sensing circuit means and to the output signal fromthe detector circuit means for locking the discharge control meansagainst deviation during the refill operation and during the time ofsaid predetermined excessive excursions. .Iaddend. .Iadd.16. Weighfeeding apparatus as in claim 15, wherein said electrical signalexhibits excessive excursions in response to disturbances impinging uponsaid weighing means which produce forces other than the forces resultingfrom the weight of the substance in the container, or from the changesin such weight, wherein said detector circuit means produces an outputsignal for each excursion of said electrical signal which has anacceleration or deceleration in excess of a predetermined value, andwherein said responsive means locks the discharge control means againstdeviation while said excessive excursion continues. .Iaddend. .Iadd.17.Weigh feeding apparatus as in claim 16, wherein said discharge meansconstitutes a double auger mechanism for maintaining a constantvolumetric feeding of the substance while said responsive means isoperating to lock the discharge control means against deviation..Iaddend. .Iadd.18. A weigh feeding apparatus comprising a container fora prefilled substance, means for discharging the substance from thecontainer at a controllable rate, means for weighing the container andits contents and for producing an electrical signal proportional to theweight, said electrical signal changing in value as substance isdischarged from the container and the weight of its contents decreases,said electrical signal changing in value more rapidly and exhibiting anexcessive excursion for each disturbance which is sensed by saidweighing means as a more rapid change in weight, means actuated by saidelectrical signal for controlling the discharge of the substance fromthe container, circuit means for providing protection against excessivedisturbances including detector circuit means actuated by saidelectrical signal for producing an output which is responsive topredetermined excessive excursions of said electrical signal, and meansresponsive to said output for locking the discharge control meansagainst deviation during the time of said excessive excursions..Iaddend. .Iadd.19. Weigh feeding apparatus as in claim 18, wherein saiddetector circuit produces an output for each change of said electricalsignal beyond a predetermined amount, from one instant in time to thenext, and said responsive means is for locking said discharge controlmeans against deviation during the time such change occurs. .Iaddend.